Glazing unit with transparent filler

ABSTRACT

A glazing unit has a at least one self-supporting insert of light-transmissive insulation material in the form of honeycomb arrangement of cells sandwiched in a gap between a pair of glass lites. A granular, light-transmissive, thermally insulating filler, such as silica aerogel, substantially fills the cells.

FIELD OF THE INVENTION

This invention relates to the field of glazing, and in particular toinsulated glazing units, typically of the type employed in largebuildings, and to a method of making such glazing units.

BACKGROUND OF THE INVENTION

It has long been the practice in the building industry to employdouble-glazed (or multiple-glazed) units as part of the wall of largebuildings, such as office towers. While such units may be transparent,when they are used as windows, it is becoming increasingly popular toemploy light diffusing units as part of the wall structure in order toincrease the amount of natural light entering the building and thusdecrease the artificial lighting requirements.

The glass industry uses sealed insulated glass units as a standardbuilding block for windows and curtainwall. These are made up of twoparallel glass panes, known in the industry as lites, which areseparated by a spacer and sealed by a bead of sealant, typicallysilicone or hot-melt butyl rubber around the perimeter. These units arefilled with air or inert gas which expands and contracts as the unitsare heated or cooled. The resultant pressure changes displace the litesof glass, and give the unit a concave or convex distortion. In normaloperation temperature cycling and resultant distortion occurs on a dailybasis.

Energy conservation in buildings is of prime importance. The thermalinsulating properties of conventional glazing units are determined bythe gap. Insulation value increases in proportion to gap because moreair results in less conductive/convective heat transfer. Radiation,which typically accounts for slightly less than 50% of heat transfer, isnot affected by a thicker gap, and therefore the proportionalityconstant is less than 1. The increase in insulation only occurs untilthe gap has a thickness of about ⅝″, at which point convective movementof air increases heat transfer at a rate that cancels any increase ininsulation.

One material that has a number of attractive properties for use inglazing applications is silica aerogel. One such silica aerogel is soldunder the name Nanogel™ by Cabot Corporation. This is a sparse silicamatrix with a very high percentage (95% or more) void fraction. It istypically made by creating a silica alcogel (silica gel with alcohol asthe liquid rather than water) and then removing the alcohol. This mustbe done at supercritical conditions in order to avoid creating surfacetension effects which would collapse the gel into a denser material(non-supercritical fluid removal would create the common dehydratedsilica gel particles which are used as dessicants, rather than aerogel).

silica aerogel is made of silica, it is as permanent and colorfast asglass itself. It is also one of the best insulating materials known(this is a function of the thermal infrared radiation absorptionabilities of silica and the ultrafine (<50 nm scale) structure. Becausesilica does not absorb visible light, and the physical inhomogeneitiesof the gel structure are much less than a wavelength of light (50 nm vs500 nm wavelength for green light), silica aerogel can be highlytransparent. Being 95% void, silica aerogel has an index of refractionthat is very close to air, so there is little surface reflection orrefraction and therefore granular material can effectively transmitlight without scattering.

Despite the promise, silica aerogel has a number of challenges. First,despite having been discovered a century ago, it is very difficult tomake monolithic aerogel that is perfect enough to work as a component ina vision window, nor is it known how to make monolithic aerogelcost-effectively. As a result silica aerogel has been relegated todaylighting applications. Several manufacturers make plastic glazingproducts or rolled glass, where it is silica areogel is used as aninsulating fill.

It would be desirable to improve the insulating properties without acorresponding increase in gap size.

SUMMARY OF THE INVENTION

One way of improving the thermal insulating properties of a glazingunit, particularly if transparency was not critical, as in the case oflight-diffusing units, would be to insert an insulating lighttransmissive filler material, such as silica aerogel, in the gap,particularly one having absorptive properties, so as to reduce theamount of radiation. It has however proved not feasible to do thisbecause of the bulging effect noted above. If such a unit were simplyfilled with granular aerogel, convex distortion would create a greatervolume in the centre and the material would settle, creating a permanentbulge in the middle and void at the top. The use of an adhesive to coatthe particles and cement them together is undesirable because it wouldalter the index of refraction of the particles and greatly increaselight scattering, thereby reducing light transmission.

According to the present invention there is provided a glazing unitcomprising a pair of opposed glass lites defining a gap therebetween; atleast one self-supporting insert of light-transmissive insulationmaterial sandwiched in said gap between said glass lites and being inthe form of honeycomb arrangement of cells; and a granular, thermallyinsulating, light-transmissive filler substantially filling said cells.The honeycomb permits the use of a larger dead air gap, for example2.5″, and also the honeycomb significantly reduces radiant heattransfer, resulting in a significantly increased R value.

The light-transmissive honeycomb is used to build a structure to retainthe granular translucent insulation, eliminate the effects of glassmovement, and reduce the effect of any actual settling. By subdividingthe gap into small compartments, any actual settling will createinsignificant gaps in numerous small cavities. Any reduction (which willbe slight in any case) in insulation value is spread uniformly over thearea. Had the gaps been consolidated, these effects would have createdan unsightly gap at the top of the unit which would also be a thermalbreach, possibly causing condensation.

It will be understood that additional lites and inserts could be added.For example, the unit could be a triple glazing unit with insertspresent between each pair of lites. Also, there could be more than onelayer of inserts between each pair of lites, or else the inserts couldbe formed in a tile structure.

The filler should normally be transmissive of visible light andabsorptive of thermal radiation. A fine granular silica, such as silicaaerogel is ideal for this purpose. The granules have a characteristicsize which is in the sub-millimeter range, but the material has amicroporous structure with a characteristic size in the order of 50 nm,i.e. less than the wavelength of light. The granules have a low index ofrefraction, which results in minimal scattering at the granuleinterfaces. The microporous structure, wherein the micropores have asize less than the wavelength of light, results in minimal scatteringwithin the granules. Silica absorbs infrared radiation, thereby reducingthe radiative component of heat transfer, and the intra-granular spacesare far too small to permit air convection. Other similar materials withinfrared radiation absorptance and low thermal conductivity and diffuselight transmittance can be used.

Since the glazing unit is designed for use in diffuse light situations,the internal components need not be completely transparent. It issufficient that they be light-transmissive, that is translucent ortransparent. It does not matter if they transmit light diffusely.

A light transmissive veil or containment layer, for example, ofnon-woven fiber glass, should normally be inserted between the honeycomband the glass lites and bonded to the honeycomb material to contain thefiller, although in a less preferred embodiment it is possible to usethe glass lites directly as the containment layer. The containment layercan also be plastic.

The honeycomb material should be sufficiently rigid to beself-supporting in combination with the filler and containment layers.It can be made of plastic. A suitable material is sold by AdvanceGlazings Ltd. under the name InsolCore™.

In another aspect the invention provides a method of making a glazingunit, comprising providing at least one self-supporting insert oflight-transmissive insulation material in the form of honeycombarrangement of cells; substantially filling the cells of said at leastone self-supporting insert with a granular, thermally insulating, lighttransmissive filler material; and sandwiching said at least one insertbetween a pair of glass lites.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail, by way of exampleonly, with reference to the accompanying drawings, in which:

FIGS. 1A to C show the effects of temperature on a double glazing unit;

FIGS. 2A and B show the effect of settling of a granular material withina double glazing unit;

FIGS. 3A and B show a transparent honeycomb structure with translucentfiller; and

FIG. 4 is an exploded view of a glazing unit in accordance with oneembodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1A to 1C show the effects of temperature on a glazing unit havinga pair of opposed glass lites 10 and an internal air gap 12. Uponheating the structure bulges in the middle (FIG. 1A) and upon cooling itbecomes convex (FIG. 1C). The structure only has its parallelconfiguration (FIG. 1A) at its nominal operating temperature.

FIGS. 2A and 2 b show what happens when the gap is filled with a fillermaterial 14, such as silica aerogel. Initially, the glass lites 10 areparallel (FIG. 2A), but after a period of time the filler settles, andthe lites bulge as shown in FIG. 2B.

FIG. 3A shows a transparent honeycomb structure 16 with a thicknessapproximately equal to the nominal gap between lites of the insulatedglass unit, preferably about ½″. This is a self-supporting honeycombstructure consisting of an array of cells 22 (see FIG. 3B) about 1 cmsquare extending completely through the structure. The honeycomb can bemade of any suitable plastic material. As noted, a suitable material isInsolCore® by Advanced Glazings Ltd.

A single non-woven glass fiber or plastic containment layer 20 is thenbonded to one side of the honeycomb structure 16. This may be made ofany suitable transparent or translucent film or sheet, or a fabric withsufficiently fine mesh size to retain the granular transparentinsulation, or combination thereof. The resulting structure is thenplaced on a flat surface with containment layer 20 down and open cellsup. The cells are then filled completely with granular tranlucentinsulation 14, such as silica aerogel, (for example, by overfilling andtrowelling). Then a second light tranmissive containment 20 layer, whichalso may, for example, be of non-woven fiber glass or plastic, is bondedto the top of the honeycomb structure. This creates a self supportinglight diffusing translucent insert as shown in FIG. 3A.

The structure shown in FIG. 3A can then be inserted between a pair ofglass lites, which can be sealed around their edges in a conventionalmanner, to form a complete insulated glazing unit, thereby diffusinglight and reducing heat transfer. FIG. 4 shows the resulting product,where the non-woven fiber glass layers 20 also serve as containmentlayers.

In alternative embodiment, the filler can be retained directly in thehoneycomb by the glass lites, which can be bonded directly to thehoneycomb structure. Furthermore, one or more additional layers ofmaterial can be placed between the lites and the insert to improve lightdiffusion, control light transmittance, or alter the aesthetics of thefinal product. This can be a non-woven fibreglass veil, such as AdvancedGlazings Ltd.'s AGL300. This layer may be simply sandwiched between theinsert and the lite of glass and thereby held in place by friction, orpreferably, bonded to the glass in order to obtain optimal stability andflatness and prevent wrinkling.

The insert 16 may be bonded to one or both lites of glass in order toprevent movement or creep over time, by use of a suitable adhesive.

EXAMPLE

A glazing unit was made using ½″ thick IncolCore™ honeycomb insert, anAGL401 non-woven fibreglass veil as containment layers, cabot nanogelinsulation, and clear ¼″ glass forming the lites. An AGL 300 veil wasbonded to the lites as described in our copending Canadian applicationno. 2,510,947, with Edgetech IG's Triseal® Superspacer® and TremcoProglaze II silicone.

A single insert of dimensions equal to the air gap may be used, oralternatively multiple smaller tiles may be used. Tiles or full-sizedinserts may be the full thickness of the airgap or may only comprisepart of the thickness of the gap, and other materials such as air orsparse white fibre can be used for the remainder. Such inserts may beused in fibre reinforced plastic panels such as kalwall www.kalwall.com,or in rolled channel glass, or between sheets of plastic.

In another embodiment honeycomb material is bonded directly to a lite ofglass. This glass is dual purpose, acting as both containment layer andinsulated glass unit lite. Bonding is via a suitable adhesive whichshould be non-yellowing and have sufficient long term adhesion to bothglass and honeycomb, such as UV curing acrylic adhesives. A lightdiffusing layer may be incorporated as well.

Honeycomb is then filled with Granular translucent insulation. A secondnon-glass containment layer is bonded to honeycomb via adhesive or heatseal. A second lite of glass is cleaned, and a spacer attached toperimeter. Glass honeycomb structure filled with granular translucentinsulation is used as second lite to fabricate insulated glass unit.

The resultant insulated glass unit can ‘breathe’ while the honeycombstructure retains the granular translucent insulation without movementor settling.

In yet another embodiment the lites serve directly as the containmentlayer. Structural adhesive is used to bond the glass to the honeycombinsert and prevent the granular material from distorting the glass.Spacing between glass is thereby maintained by honeycomb. This resultsin a glass-honeycomb-glass structural panel that has some desirableproperties.

It has been found that glazing units in accordance with embodiments ofthe invention can achieve insulation values of R5 with a gap as small as½″ in comparison with a glazing unit employing an air or inert gas airfiller, where the gap would need to be in the order of 2½″ to achieve asimilar result.

While ½″ is a suitable thickness for the gap, since generally the for anair filled glazing unit the heat transfer is minimized, it will beappreciated that other gap sizes can be selected. With the filledglazing unit that blocks convection, it is possible to increase thethickness and simply add more and more fill to get an increased R-valuein return. However, some practical limits are imposed, such as the costof the fill, and framing compatibility (the glass industry is builtaround 1″ thick units, such as ¼ glass, ½ gap, ¼″ glass. They can handlethicker units, but it becomes less standard and therefore typically moreexpensive.

Another important issue is the ability to seal a unit. The variablepressure differential between the inside and outside is more of problemwith thicker units, as the glass must move (convex or concave) by a % ofthe gap to relieve the pressure, and the absolute displacement istherefore bigger for thicker gaps. This creates more stress on the glassand seals. In practice, ½″ gap works with conventional seals, but 1″ gap(triples, for example with two ½″ gaps) units are less reliable and itis not wise to seal units with greater than a 1″ gap.

When the thickness is greater than 1″, for instance in the case of 2.5″units with honeycomb insulation, venting is generally required. Ventingworks in translucent units but not in clear vision glass units. Ventingis not standard practice, but does not create a significant technicalproblem.

1. A sealed glass glazing unit comprising: a pair of opposed glass litesdefining a gap therebetween; at least one self-supporting insert oflight-transmissive insulation material sandwiched in said gap betweensaid glass lites and being in the form of honeycomb arrangement ofcells, the insert being unconnected to either glass lite; a granular,thermally insulating, light-transmissive filler substantially fillingsaid cells, wherein the insert serves to stabilize the filler; and alight transmissive, porous containment layer bonded onto each side ofsaid insert, the porous containment layer having a pore size suitable tocontain the granular filler and permit airflow through both the porouscontainment layer and the granular filler.
 2. The glazing unit of claim1, wherein said granular light-transmissive filler is absorptive ofinfrared radiation.
 3. The glazing unit as claimed in claim 2, whereinsaid granular light-transmissive filler has an internal microporousstructure having a characteristic size less than the wavelength oflight.
 4. The glazing unit as claimed in claim 1, wherein saidcontainment layer is non-woven fiber glass.
 5. The glazing unit asclaimed in claim 3, wherein said microporous structure has acharacteristic size in the order of about 50 nm.
 6. The glazing unit asclaimed in claim 5, wherein said granular light-transmissive filler issilica.
 7. The glazing unit as claimed in claim 1, wherein saidtransparent granular light-transmissive filler is a silica aerogel. 8.The glazing unit as claimed in claim 1, wherein at least two layers ofsaid inserts are located within said gap.
 9. The glazing unit as claimedin claim 1, further comprising a light transmissive veil located betweenat least one of said lites and said insert.